Wave Pounding: Steep waves have high energy level.
These waves break when they hit sea walls of the foot of a cliff,
hence their energy is released upon impact, resulting to shock
waves of up to 30 tonnes per m2. This constant
bombardment is so destructive that sea walls in the UK need
replacing every 25 years.

Hydraulic Pressure: As a wave approaches a cliff air
can become trapped between them, and find its way into joints.
The pressure increases in this air trap as the wave gets closer,
thus damaging the cliff face over time.

Abrasion/ corrasion: The most effective erosion method,
when the load carried by the wave is hurled at the cliff face,
thus eroding it, it can also damage other sea defences.

Attrition: Chunks of rock eroded from the cliff faces
are broken down to more rounded particles: sand.

Corrosion/solution: Includes the dissolving of
limestones by carbonic acid, found in sea water, evaporation of
salt crystals within the cracks of a rock, thus expanding it and
weakening its structure. Several rock types are eroded by
seawater or spray and secretions from pioneer blue-green algae
also contribute to corrosion.

Sub-Aerial; Other, non-marine processes ware down the
slope, Rain can erode the cliffs through direct contact,
throughflow and surface run off. Combine this with the effects of
wind and the result can be mass movement, either soil creep, on
gentle slopes, or landslides on more steep slopes.

Human activity; Removal of beach material and
persistent development on the tops of cliffs have contributed to
more rapid soil erosion.

The effects of erosion may be reduced, locally by the
construction of sea defences. Without human presence and
interference many of these defences would not be required.

Factors affecting the rate of erosion

Breaking point of wave: The maximum energy is released
when the wave hits the cliff at the moment of its collapse. If it
hits the cliff before it breaks less energy is released since it
never reaches the higher energy level. If the wave breaks before
it hits the cliff then the energy level is less since it looses
energy travelling over the beach.

Wave steepness; Waves that are created nearer the coast
are steeper and thus have more energy, whereas swell, which is
created kilometres offshore, have less energy, and thus less
erosive capabilities.

Depth of sea, length and direction of fetch, configuration
of coastline: The more steep the shelving of the beach is the
higher and steeper the waves created. The longer the fetch, the
more time the wave has to collect energy from the wind, hence the
more energetic the wave. Headlands with vertical cliffs
concentrate energy by wave refraction.

Supply of beach material: Although this material is
used to erode the cliffs, a surplus actually absorbs some energy
off the waves, conserving the cliff face.

Beach Width: The more beach material a cliff has a
readily available supply to, the wider the beach, hence the more
protection the cliff receives from erosion.

Rock Resistance, structure and dip: The strength of
coastal rocks effects the rate of erosion, for example coastal
areas where glacial till was deposited is eroding rapidly. Even
Surtsey, when it first emerged from the depths of the Atlantic
Ocean in 1963, it was only the lava that ensured the
islands survival. Well jointed or fault ridden rocks are
also highly susceptible to erosion. The horizontal or vertical
rock structures produce the steepest cliffs, and where the rock
dips up and away from the sea. Where different rocks of varying
resistance lie on top of each other, erosion is also rapid.

Erosion Landforms

Headlands and Bays: Mostly form in areas of varying
rock resistance, firstly the rocks of lower resistance are
eroded, forming bays and leaving headlands where there are
outcrops of more resistant rock. These headlands then receive the
higher energy waves and thus a beach develops in the bay, further
protecting it from erosion.

Wave Cut platforms: A wave cut notch results
when a high steep wave breaks at the foot of a cliff. After many
repeats of this procedure, the cliff collapses and leaves a wave
cut platform with a slope angle <4o. Where
there has been a drop in sea level, former waves cut platforms
remain, and are called raised beaches.

Caves,
blowholes, arches and stacks: Where cliffs are composed of
resistant rock, wave action attacks the lines of weakness
sometimes creating a steep sides, narrow inlet, called a geo, or
where the cliff is undercut, a cave might form. These
caves may also be enlarged by a combination of marine erosion
processes, vertical erosion may also occur, hence blowholes are
formed. However erosion is more typically backward through the
exposed headlands to form arches and stacks.

Transportation of beach material

Up and down the beach: Constructive waves deposit
material on the beaches whereas steep, destructive waves comb
material back into the sea.

Longshore (littoral) drift: Usually wave crests
approach the coast at and angle that is determined by the
local configuration of the coastline. This angle creates a
nearshore current called Longshore (littoral) drift,
this is capable of moving large quantities of material in a
down-drift direction. This drift is commonly is in one
direction, for example in south coast of England where there
is a predominant movement of material eastward. To prevent
the loss of material through this effect groynes are
built to hold back material, and make the beach thicker. The
action of long drift and the implication of groynes are
illustrated in the diagram above. However these groynes hold
back material making an area grow a wider beach, hence
increasing tourism revenues, however this also leads to a
depletion of material downshore.